The present invention relates to a new and improved apparatus for controlling and for signal transmission in conveyor installations or the like.
In its more specific aspects the invention relates to a new and improved apparatus for controlling and for signal transmission in conveyor installations or the like which is of the type including a number of conveyors movable along a track system or path of travel. Between the individual conveyors and a central system control there is provided a stationary transmitting and receiving installation, the receiving component or section of which comprises receiving circuits each of which is operatively associated with a respective track section and provided at a respective control location. Installations of such type are employed to control the movements of individual conveyors along their tracks or travel paths, for example, in floor-level conveyor installations and to transmit signals between the conveyors and a central system control or central control station.
A number of different types of such apparatus is already known which, in principle, rely upon functionally-specific layout elements which are arranged along the track or travel path and form an interface between the stationary control and the mobile conveyors. Exemplary of such equipment are control frequency loops to establish the track network, start-stop frequency loops for controlling the travel of the conveyors, presence detector loops for detecting the conveyors in their layout, floor sheet metal or metal plating arrangements for transmitting constant data to the conveyors. The start-stop loops and the presence detector loops are also used in pairs for bidirectional signal transmission between the conveyors and the stationary control by using frequency modulation. What is disadvantageous for such systems is the increased expense for the installation and the electronic components which results from the multitude of layout elements which are required. Additionally, the amount of data which can be encoded when using conventional floor metal plating arrangements is limited and frequently insufficient, for example, for identifying locations in installations working with an expansive track or travel path network.
An installation for the inductive signal transmission as known, for example, from European Patent Publication No. 0,053,599, is installed between a stationary transmitting and receiving station and individual conveyors. An induction loop laid along the track or travel path forms a transmission loop which is connected to the transmitting component or section of the transmitting and receiving station, while the receiving component or section comprises a number of receiving units for separate connection to reporting back loops, each of which is operatively associated with a respective track section.
For each of the two transmission directions there is thus required a special kind of layout element, i.e. a transmission loop and a reporting back loop. Furthermore, in such installations there is present the problem of cross-communication since the same frequencies are used for the transmission loop and for the reporting back loops. Therefore, to avoid expensive shielding the transmission loop and the reporting back loops must be arranged in planes extending perpendicular to each other, at least one of which contains the longitudinal axis of the loop associated with the other plane. Of course it is also necessary that the transmitting and receiving antennaes on the conveyors assume corresponding positions relative to each other and relative to the loops. There thus results a lack of freedom in the arrangement of the layout elements and the conveyors which constitutes a significant disadvantage. Also, the inductive signal transmission installation cannot de-centrally store and transmit constant data as required, for example, in partially autonomous operation by the conveyors for controlling their function and for determining their location within the layout. Therefore, all data required for the control of the conveyors has to be transmitted over the entire length of the transmission channels between the transmitting and receiving stations and the individual conveyors. In large-size installations of this type the limits of the available transmission capacity will be reached very soon notwithstanding the directional separation or isolation of the transmission channels.
In a system for identifying articles and persons and for data transmission as known, for example, from European Patent Publication No. 0,033,124, a reader is provided and a responder or answering device is arranged at the location of the data storage. The responder transmits reading signals arriving at the responder back to the reader with a time-delay corresponding to the data content. While such a system is specifically designed for data transfer which is safe from malfunction and falsification, this is ensured for only within the normal question-and-answer operation between the reader and the responder. While in this prior art system constant data like, for example, the location code in conveyor installations can be automatically transmitted and in a decentralized fashion to the conveyors, there is no possibility to interconnect the conveyors and the central system control with respect to the signals transmitted therebetween, as such is required when the conveyor installation is partially autonomously and centrally controlled.